Extreme Temperature Diary- Saturday April 27th, 2024/Main Topic: Summerlike Temps Will Come Early for the Eastern and Southern U.S.

Sudden summer: D.C. could see its first 90-degree day this year Monday – The Washington Post

Sudden summer: D.C. could see its first 90-degree day this year Monday

It would arrive about 2 weeks ahead of schedule. Some records could be broken.

By Ian Livingston

Chillier than normal weather ruled the Washington region for most of the last week — with highs mostly in the 60s. But mother nature’s heater is about to turn on full blast.

The District could see high temperatures of 90 degrees Monday and Tuesday as the first surge of summer heat swells over the region. Temperatures this high would be 15 to 20 degrees above normal.

To hit 90 for the first time in late April would be about two weeks earlier than normal but not all that surprising considering 2024 has been one of Washington’s warmest years on record so far. Recall that it hit 80 degrees in January for the first time on record.

If the District reaches 90 on Monday, it will be the earliest first instance since 2017, when it first hit 90 on April 29.

With an early season heat dome developing over the eastern United States starting late this weekend, the area is poised to post a streak of five or six days with highs in the 80s or higher. This is fairly impressive for the time of year when average highs are still in the low 70s.

Monday appears to have the highest chance of reaching 90, but Tuesday could reach the mark as well. Some model simulations suggest additional chances to hit 90 late next week (around May 2 or 3).

Here’s a summary of model projections for high temperatures on Monday and Tuesday:

  • American GFS — 89 Monday / 84 Tuesday
  • European ECMWF — 87 / 90
  • Canadian — 88 / 86
  • ICON — 88 / 86
  • Machine learning average — 92 / 90

This time of year, when the air is still relatively dry, daytime temperatures sometimes end up higher than projected, particularly if clouds are few and winds come in from the west.

An unusually early taste of summer

Washington’s normal first 90-degree day is around May 16; it’s around May 14 in Baltimore and May 19 at Dulles International Airport.

On days when the urban centers just nick 90 degrees, surrounding suburbs often aren’t quite as hot, with highs typically in the mid- to upper 80s.

Washington’s earliest 90-degree day on record occurred on March 22, 1907. More recently, it hit 90 as early as April 6, 2010, setting the stage for a record-tying 67 days at or above 90 that summer.

D.C.’s latest first instance of 90 degrees waited until July 12 in 1979.

Last year’s first 90 held off until June 2, which was about two weeks later than normal.

Records at risk

The hot weather early next could challenge records. Monday’s record high in Washington is 91 (from 2017) and 92 on Tuesday (from 1942).

Record-breaking heat at Dulles Airport is more probable because the numbers to beat are lower (records at Dulles only date to 1963 compared to the 1870s in Washington). Monday’s existing record high is 89 (from 2017), and Tuesday’s is 86 (from 2017).

Record-warm lows are possible on Tuesday as it’s not forecast to get any cooler than the low- to mid-60s in the morning. The warmest lows on record for the date are 67 in Washington, 66 at Dulles and 63 in Baltimore.

More to come?

After flirting with 90 degrees on Monday and Tuesday, warmer than normal weather is favored to persist through the workweek and perhaps into the weekend before temperatures return closer to normal.

But odds are any cool-down won’t last long. This is the fourth-warmest year on record to date and a hotter than typical summer is anticipated.

The trend toward higher temperatures in Washington — the city has warmed about 5 degrees since the late 1870s — is the result of human-caused climate change. Both the burning of fossil fuels and urbanization are driving temperatures higher.

Jason Samenow contributed to this report.

By Ian Livingston Ian Livingston is a forecaster/photographer and information lead for the Capital Weather Gang. By day, Ian is a defense and national security researcher at a D.C. think tank. Twitter

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